The present invention relates to the field of manufacture of composite high pressure vessels.
Composite high pressure vessels and methods of manufacture thereof are well known in the prior art. By way of example, nonmagnetic scuba tanks had been manufactured by winding a resin impregnated high strength filament on a mandrel comprising an inert liner and one or more end pieces or polar rings for providing a means for air communication with the vessel. Normally winding precedes back and forth across the liner, encircling the polar ring in some manner to integrate the polar ring into the overall structure, the resin being cured on completion of the winding to complete the pressure vessel. In some instances, the inner lining may be preformed by blow molding or the like, and is sufficiently self-supporting, particularly when slightly pressurized to itself serve as the winding mandrel. In other instances, some form of collapsible mandrel may be used, or alternatively, a readily dissolvable mandrel may be used which, of course, is dissolved out of the finished bottle after curing the resin.
The foregoing techniques work well for the manufacture of relatively small pressure vessels but are not suitable for large pressure vessels. In particular, an inert liner for a large pressure vessel is not sufficiently self-supporting to adequately serve as a winding mandrel unless the liner is unreasonably thick. In that regard, liner thicknesses need not be proportional to pressure vessel size, as in any event the liner thickness need only be sufficient to be impervious to the fluid or gas to be contained therein. Collapsible mandrels, on the other hand, are relatively expensive at best, and are particularly expensive for large sizes. Similarly, dissolvable mandrels in large sizes are unreasonably expensive and time consuming to dissolve away.